Radiative cooling induced coherent maser emission in relativistic plasmas

TL;DR

This study uses high-resolution simulations to show that relativistic plasmas in strong magnetic fields can spontaneously generate long-lasting coherent maser radiation through electron cyclotron instability, relevant to astrophysical phenomena.

Contribution

First ab initio kinetic simulations demonstrating coherent maser emission in relativistic plasmas with radiative cooling, revealing new insights into plasma behavior in astrophysical environments.

Findings

Relativistic plasmas generate coherent linearly polarised radiation.

Radiative losses influence the saturation of the electron cyclotron maser instability.

Plasmas can amplify coherent radiation for extended periods.

Abstract

Relativistic plasmas in strong electromagnetic fields exhibit distinct properties compared to classical plasmas. In astrophysical environments, such as neutron stars, white dwarfs, AGNs, and shocks, relativistic plasmas are pervasive and are expected to play a crucial role in the dynamics of these systems. Despite their significance, both experimental and theoretical studies of such plasmas have been limited. Here, we present the first ab initio high-resolution kinetic simulations of relativistic plasmas undergoing synchrotron cooling in a highly magnetized medium. Our results demonstrate that these plasmas spontaneously generate coherent linearly polarised radiation (independently of the electron/positron ratio), in a wide range of parameters, via the electron cyclotron maser instability, with radiative losses altering the saturation of this instability. This enables the plasma to continously amplify coherent radiation for significantly longer durations of time. These findings highlight fundamental differences in the behaviour of relativistic plasmas in strongly magnetized environments and align with astronomical phenomena, such as pulsar emission and Fast Radio Bursts.